The present invention is relates to sealed tray packaging machines and specifically the registration, of the film seal and the tray top face, in such packaging machines. Sealed tray packaging machines usually package goods in a tray which is then sealed on its top face with a heat sealable thermoplastic film heat molded onto the edge of the tray. Often the top face sealed film has a see through window or carries printing or other indicia. Usually the film is fed in a ribbon from a large roll with the indicia sequentially duplicated on the ribbon in repetitive segments corresponding to the spacing, established by the packaging machine, for each tray.
Registration is the process of synchronizing machine operations for the proper positioning of the sealing film material over each tray during the sealing operation. It is a process for the coordination of the timing of a packaging machine operations and the spacing of the juxtaposed members so that each film section (segment), taken off of the ribbon from the roll, is properly positioned when sealed to a respective tray. Often the film carries a series of recognition marks, i.e., "registration marks", for indicating those relative positions of each tray top segment printed on the film. Thereby, each film section (segment) is properly centered over a tray when the sealing operation is performed.
The synchronization of packaging machine operations and the synchronization of tray sealing packaging machine operations has always been an engineering concern with conveyor belt type machines. With the advent of sealed tray packaging machines and packaging machines producing heat sealed compound packages, registration has also been a concern.
Vetter, U.S. Pat. No. 3,979,877, shows a packaging machine with web registration. Registration marks carried on the film are sensed and the reciprocal drive which advances the product tray conveyor is controlled to maintain registration. This control increases the drive extension to increase the step movement distance. Thus registration is maintained by controlling conveyor operation with sensed film advance.
Eaves, et al., U.S. Pat. No. 4,574,566 show a wrapping machine which has independent closed-loop controlled, servo motor drive circuits for each of the film drive, the product (conveyor) drive, and the cut/seal head operation. A film "eye spot" sensor (photo eye) provides a registration signal (miss-registration signal) which is fed to the product drive controller circuit. The product drive signal is adjusted to change the product drive speed to bring the product into registration with the film advance. Extensive control logic is implemented in electronic processor routines and stored logic programs.
Heaney, U.S. Pat. No. 4,722,168 shows a registration control for a wrapping machine. A photoelectric sensor and a radiation transmitter sense film position with respect to the conveyor and package position. When miss-registration occurs, the sealing operation of the machine is suspended. The film is advanced to bring the film into registration with the machine. The amount of film advancement is calculated by a computer which then controls the film drive during said film-to-machine adjustment period. When the proper registration is achieved, the normal wrapping machine operation is resumed.
Wylie, U.S. Pat. No. 4,744,202 shows a method and apparatus for controlling the relative position of a web film to the synchronization cam of a sealing machine. Registration marks on the film are sensed by a photocell circuit. The speed of the film drive (film advancement) is adjusted by applying a brake to the film drive subsystem.
Barker, U.S. Pat. No. 4,807,420 shows a horizontal conveyor form fill and seal packaging machine driven by a digitally controlled stepper motors. The product drive and the web drive individual stepper motors operations are controlled from a central processor unit (CPU). The drive signals (speed control) to each of these motors is adjusted by the CPU in response to product and web sensors.
Cherney, U.S. Pat. No. 4,860,522 discloses a machine with individual drives for film and conveyor movement. Film movement is adjusted by changing the drive speed which results in a change in the amount of film pull. A computerized film registration mark and window monitoring system calculates for small changes in film drive speeds. These speeds are then computer controlled.
Francioni, U.S. Pat. No. 4,914,889 shows a machine whose operation is synchronized from a single drive motor thorough electronically controlled positioning. A drive take off for the conveyor and a drive take off for the film advance are adjusted by the control of a belt transmission system. Miss-registration is compensated for by adjusting the drive speed of the conveyor and the drive speed of the film feeder with respect to one another.
Muller, U.S. Pat. No. 5,642,604 shows a spacing conveyor for moving cans (fill packages) through a packaging machine. The movement of the packages can be adjusted by adjusting the speed of the sprocket conveyor which moves the cans.
Manly, U.S. Pat. No. 5,727,366 discloses a registration control, which is computer software logic implemented, for controlling a continuous operating package filling machine. The position and speed of the packaging material is adjusted for miss-registration. A servo motor driven nip roller system is used to feed the film to the seal station. Registration marks along the film are monitored for miss-registration. The movement (speed) of the servo motor drive is computer controlled to index the film registration forward or backward (faster or slower movement) in synchronization with the operation of the packaging machine.
With improvements in computer miniaturization, reduction in cost of microprocessors, increased sophistication in computer programming and more sophisticated electric and digital stepping motor controls, the industry has move registration in packaging machines into ever more sophisticated designs. These structures are more expensive to build and to maintain. They require calibration, and are subject to loss of such calibration from rough handling and wear.
What is desired a registration system and method of registration for a packaging machine, specifically a sealed tray packaging machine, which is less complicated in its logical controls and which is durable enough to maintain its function when subjected to rough handling and wear.
What is further desired is such a sealed tray packaging machine wherein its drive operational control structure assures that the various operations of the machine always remain in synchronization.
What is further desired is registration correction in such a sealed tray packaging machine of the sealing film positioning, respective to tray positioning, which provides such correction without effecting the synchronized operation of the machine.